Lubricating oil composition



United States Patent Cfiice LUBRICATING OIL COMPOSITION Warren Lowe, Berkeley, Calif., assign'or to California Research Corporation, San Francisco, Calif., a corporation of Delaware I No Drawing. Application December 27, 1954 Serial No. 477,955

3 Claims. (Cl. 252-3345) This invention relates to a new lubricating oil composition. More particularly, the invention is concerned with a novel lubricant composition having superior corrosion inhibiting properties.

During their normal service, lubricating oil compositions tend to become corrosive to metals. This is particularly so when they are employed in modern internal combustion engines which are operated under conditions involving increased temperature changes, higher speeds and reduced clearances, all of which conditions aggravate the formation of corrosive decomposition products in the oil. Alloy metal bearings commonly employed in such engines make the problem all the more serious, since they are especially subject to corrosive attack and furthermore, may have a catalytic effect on the decomposition of lubricating oils with which they come into contact, thereby causing additional corrosivity in the oil.

The addition of inhibitors to lubricating oil compositions, generally, for the purpose of improving their resistance to the formation and effect of corrosive products has not been entirely satisfactory. A great many of these additives are only moderately effective and permit the bearings and other metal surfaces coming into contact with the lubricating oil composition to be slowly but eventually corroded to a degree where interruption of engine operation for overhaul and replacement of parts becomes necessary. Furthermore, many of the more effective additives are active only for a limited period and require replenishing or a complete change of the lubricating oil composition. Still other additives, although effective as corrosion inhibitors, are so insoluble in oils of lubricating viscosity that special solubilizing or dispersing agents are necessary to retain them in the composition.

Corrosion inhibitors for lubricating oil compositions are further handicapped by the fact that oils of this type are commonly compounded with other additives such as detergents, sludge inhibitors and the like which are designed to loosen, suspend and otherwise minimize the effect of decomposition products formed in the oils during their normal service. Many of these compounding agents, besides adding to the corrosivity of the oil themselves, have an adverse effect on the activity of the corrosion inhibitors employed heretofore, and it is necessary to find inhibitors which will function in combination with them.

Furthermore, additives for the inhibition of oxidation or corrosion in lubricating oil compositions prior to this invention have generally contained some form of active sulfur. This has made such compositions undesirable for the lubrication of silver and similar metal-containing bearings which are especially susceptible to attack by active sulfur. Since silver and similar metal-containing bearings are being increasingly employed today, particularly in certain important classes of internal combustion enginessuch as marine and railroad diesel engines, it has become necessary to find a lubricant composition which is inhibited against corrosion without the use of sulfur-containing additives.

According to the present invention, a new and unusually effective lubricating oil composition having improved cor- 2,902,450 Patented Sept. 1, 1959 rosion inhibiting properties has been found comprising a major portion of an oil of lubricating viscosity and a minor portion, suflicient to inhibit corrosion, of a p-xylylenediamine salt of an acid compound selected from the group consisting of glycol boric acids and vicinal dihydroxy benzene boric acids.

The new lubricating oil composition in accordance with the present invention is characterized by remarkable corrosion inhibiting properties for metal surfaces and alloy bearings over extended periods of operation. The composition is unusually stable under normal operating conditions without the use of stabilizers and dispersing agents. There is no reduction of corrosion inhibition due to deposition of the additive. A further outstanding characteristic of the composition, however, lies in the fact that these beneficial properties are obtained without adverse eifect from other conventional additives commonly employed in lubricant compositions. The lubricating oil compositions of the invention possess still another advantage in that they are unusually effective lubricants for particular alloy metal bearings such as the silver metal-containing bearings of marine and railroad diesel engines.

The p-xylylenediamine salts of glycol boric acids or vicinal dihydroxy benzene boric acids which provide the new and unusually effective corrosion inhibited lubricat-- ing oil compositions according to the invention are novel compounds. They are prepared by the addition of p-xylylenediamine to the glycol boric acid or vicinal dihydroxy benzene boric acid. The reaction is straightforward, and the salt is obtained merely by heating a mixture of p-xylylenediamine and the glycol boric acid or vicinal dihydroxy benzene boric acid at a temperature at which reaction occurs until the reaction is complete. Stoichiometric amounts of p-xylylenediamine are reacted with the glycol boric acid or vicinal dihydroxy benzene boric acid. Preferably molar excesses of p-xylylenediamine up to 30% or more are used to insure complete reaction. Temperatures of from about 50 C. to about C. are preferred, although some reaction will occur at temperatures below and above this range, as, for example, from 25 C. up to C. and higher. Inert solvents may be used, if desired, in the reaction to facilitate the handling of materials.

The glycol boric acids and vicinal dihydroxy benzene boric acids referred to above are complexes prepared by the reaction of a mixture of boric acid and glycol or polyhydroxy benzene. The mixtures are ordinarily heated to accelerate the reaction. Although the nature of the reaction is not definitely known, it is believed that two of the hydroxyl groups of a single glycol or polyhydroxy benzene react with the boric acid to form what is commonly termed a metal chelate compound. These compounds are characterized by a claw type of structure in which one or more rings of a similar or unlike structure due to the use of mixed glycols or polyhydroxy benzenes are formed to include the boron. For contrated by the following formulae:

Di-beta glycol borates 2,902,450 3 4 R R R invention. They include hydrocarbon or mineral lubri- \l cating oils of naphthenic, paraffinic, and mixed naphthenic R G O\ and paraflinic types. They may be refined by any of B B the conventional methods such as solvent refining and 5 acid refining. Synthetic hydrocarbon oils of the alkylene I I polymer type or those derivedfrom coal and shale may R also be employed. Alkylene-oxide polymers-and their MWWWMTQYOOWOM Monmbotw'glywlmmes derivatives such as the propylene oxide polymers and their ethyl esters and acetyl derivatives in which the terminal hydroxyl groups have been modified are'also Mono-pyrocatechol borates I o o Dl-(pyrocatechol) borates wherein R'ishydrogenor a group ofhydrocarbon structure ashereinafter defined.

The glycols which are reacted with the boric acid are preferably 04- and ,B-alkanediols containing from 2 to 18 carbon atoms. Such glycols include, for example, ethylene glycol, 1,2- and 1,3-propanediol, 1,3-pentanediol, 2,3- butanediol, 1,2-hexanediol, 2.-methyl--1,3-pentanediol,1,2- and 1,3-octylene glycols including 2-ethyl-1,3-hexanediol, 1,2-dodecanediol, 2,4-diethyl-l,3-octanediol, and 2,4,6- triethyl-l,3-decanediol. Glycols containing from 6 to 10 carbon .atoms are more preferred, since they impart an optimum degree of oil solubility to the final product. ocand B-Octylene glycols such as 2-ethyl-1,2 -hexanediol and 2-ethyl-1,3-hexanediol are most satisfactory for present purposes. g

The polyhydroxy benzenes are preferably vicinal dihydric phenols such as catechol, 3,4-dihydroxy toluene, tert.-butylcatechol, cetylcatechol, and the like. They may contain additional hydroxyl groups, as for example, 1,2,4-trihydroxy benzene. Alkyl catechols containing from 2 to 18 carbon atoms in the alkyl group are at present most preferred since the compounds prepared from them possess the most satisfactory oil solubility characteristics.

The acid compounds of boric acid and glycols or polyhydroxy benzenes referred to above are more fully described in the co-pending patent application of John R. Thomas and Oliver L. Harle, Serial No. 440,264, filed June 29, 1954, now Patent No. 2,795,548. The p-xylylenediamine is a known compound and may be conveniently obtained by'the conversion of terephthalic acid to terephathalodinitrile, which may then be hydrogenated to give the p-xylylenediamine.

The p-xylylenediamine salt of the acid compound of boric acid and a member selected from the group consisting of glycols and vicinal polyhydroxy benzenes, as already mentioned, is present in the lubricating oil composition in a minor portion, sufficient to inhibit corrosion. Generally, amounts from 0.01 to about 10.0% by weight of the lubricating oil composition are very satisfactory. Lubricating oil concentrates containing larger amounts of the corrosion inhibitor, up to 30% by weight or more, constitute a specific embodiment of the invention. The unusual stability of these lubricating oil compositions is particularly adapted to the preparation of such concentrates which would not be possible with conventional additives. For present purposes, the preferred lubricating oil compositions contain from about 0.1 to 5.0% by weight. Such compositions are unusually stable and provide remarkably efiective corrosion inhibition for extended periods in the operation of internal combustion engines.

Any of the well-known types of oils of lubricating viscosity are suitable base oils for the compositions of the suitable. Synthetic oils of the dicarboxylic acid ester type including dibutyl adipate, di-2-ethylhexyl "sebacate, di-n-hexyl fumaric polymer, di-lauryl azelate, and the like may be used. Alkyl benzene types of synthetic oils such as tetradecyl benzene, etc., are also included. Liquid esters of acids of phosphorus including tricresyl phosphate, diethyl esters of decane phosphonic acid, and the like may also be employed. Also suitable are the polysiloxane oils of the type of polyalkyl-, polyaryl-, polyalkoxyand polyaryloxy siloxanes such as polymethyl siloxane, polymethylphenyl siloxane and polymethoxyphenoxy siloxane and silicate ester oils such as tetraalkyland tetraaryl silicates of the tetra-Z-ethylhexyl silicate and tetra-p-tert.-butylphenyl silicate types.

As already mentioned, the corrosion inhibiting'corripositions of this invention are outstanding in that they are unusually effective in the form of compoundedlubricating oils containing conventional additives such as oxidation inhibitors, detergents or dispersants, sludge inhibitors, pour depressants, VI improvers, antifoaming agents, rust inhibitors, oiliness or film strengthening agents, wear inhibitors, dyes and the like. A great many of these compounded oils are generally corrosive to metal surfacesand alloy metal bearings in particuIar,-a'nd it is an exceptional attribute of the present compositions whereby corrosion inhibited compounded lubricating oils are provided. 'A further very desirable feature of the compositions according to the invention is the fact that the corrosion inhibition is obtained Without any noticeable adverse etfect on the other additives, thus permitting more (efficient allaround lubrication of internal combustion engines and other types of machines where unusually severe conditions of service are more and more commonly encountered.

The following examples are submitted as additional illustrations of the invention. These examples show the preparation of the various lubricant compositions and the evaluation of their effectiveness as corrosion inhibitors. The proportions given in these examples, unless otherwise specified, are on a weight basis and include both percent and millimoles per kilogram (mM/kg.) of the various additives.

EXAMPLE I In this example the p-xylylenediamine salt of di( -2-ethyl- 1,2-hexanediol)boric. acid was prepared. 1.36 parts of p-xylylenediamine and 3.06 parts of di(2-ethyl-l,2-hex-anediol)boric acid were charged to a reaction vesselequipped with stirring and heating means. The mixture was stirred at 200 F. for about 10 minutes. The product was a viscous brown liquid which was soluble in mineral oil.

EXAMPLE II In this example a lubricating oil composition containing 1% by Weight of the p-xylylenediamine salt of di(2-ethyl- 1,2-h'ex'anediol)boric acid was prepared. 346.5 parts of a solvent refined SAE 30 mineral lubricating oil containing 10 mM/kg. basic calcium petroleum sulfonate analyzing 1.67% calcium and 36 mM/kg. sulfurized basic calcium alkyl phenate analyzing 3.10% calcium was charged to a reaction vessel equipped with stirring and heating means. 3.5 parts of the p-xylylenediamine salt of di(2-ethyl-l,2-hexanediol)boiic acid prepared in Example I was then added. The mixture was stirred at about F. for 20 minutes. The product was astable lubricating oil composition completely clear in appearance indicating uniform miscibility of lubricating oil base and corrosion inhibitor.

Other p-xylylenediamine salts of glycol boric acid compounds and lubricating oil compositions containing them were prepared in accordance with the above-described procedures. The properties of these compositions and their eifectiveness are illustrated by the following typical results of standard lubricating oil tests for determining corrosion inhibition. In the Copper-Lead Strip Corrosion Test, a polished copper-lead strip is weighed and immersed in 300 ml. of test oil contained in a 400 ml., lipless Berzelius beaker. The test oil is maintained at 340 F. under a pressure of 1 atmosphere of air and stirred with the mechanical stirrer at 1000 r.p.m. After 2 hours, a synthetic naphthenate catalyst is added to provide the following catalytic metals:

Percent by weight Iron 0.008 Lead 0.004 Copper 0.002 Manganese 0.0005 Chromium 0.004

The test is continued for 20 hours. The copper-lead strip is then removed, rubbed vigorously with a soft cloth and weighed to determine the net weight loss.

The reference oil of the compositions tested is a conventional compounded oil, namely, solvent refined SAE 30 mineral lubricating oil containing mM/ kg. of basic calcium petroleum sulfonate analyzing 1.67% calcium and 36 mM/ kg. of sulfurized basic calcium alkyl phenate analyzing 3.10% calcium. The concentrations of pxylylenediamine salt of the glycol borate complex are given in percent by Weight of the composition.

Table COPPER-LEAD STRIP CORROSION TEST The above tests show that the reference oil, a conventional compounded lubricating oil containing a representative heavy duty oil detergent additive of the alkaline earth metal petroleum sulfonate type and stabilizer of the alkaline earth metal phenate type, when used alone, gives a copper-lead strip loss of over 250 mg. The addition of 2% by weight of di(2-ethyl-1,3-hexanediol) boric acid to the reference oil in the test causes an even greater copper-lead strip loss of about 354 mg. By way of distinction, lubricating oil compositions in accordance with the invention employing only 1% of the p-xylylenediamine salt of the glycol boric acid give a very low corrosion loss of only 7.4 mg. Such outstanding effectiveness of the present compositions is all the more remarkable, since it is not shared by similar compositions containing other amine salts of glycol and catechol boric acids, including the isomeric m-xylylenediamine salt.

Although the lubricating oil compositions of the invention have been described primarily for their effectiveness as internal combustion engine lubricants, a great many other applications are also possible. Such applications include their use as turbine oils, hydraulic fluids, instrument oils, constituent oils in grease manufacture, ice machine oils and the like.

I claim:

1. A lubricant composition consisting essentially of a major portion of a mineral lubricating oil for internal combustion engines containing minor amounts of basic alkaline earth metal petroleum sulfonate and basic sulfurized alkaline earth metal alkyl phenate which is normally corrosive to alloy bearings and a minor portion, sufficient to inhibit corrosion of a p-xylylenediamine salt of a diglycol boric acid in which the glycol groups are identical aand ,B-glycol groups containing from 6 to 10 carbon atoms in each glycol group.

2. A lubricant composition consisting essentially of a major portion of a mineral lubricating oil for internal combustion engines containing minor amounts of basic calcium petroleum sulfonate and basic sulfurized calcium alkyl phenate which is normally corrosive to alloy bearings and a minor portion, sufiicient to inhibit corrosion, of a p-xylylenediamine salt of di(2-ethyl-l,3-hexanediol)boric acid.

3. A lubricant composition consisting essentially of a major portion of a mineral lubricating oil for internal combustion engines containing minor amounts of basic calcium petroleum sulfonate and basic sulfurized calcium alkyl phenate which is normally corrosive to alloy bearings and a minor portion sufificient to inhibit corrosion of a p-xylylenediamine salt of di(1,2-hexanediol) boric acid.

References Cited in the file of this patent UNITED STATES PATENTS 1,975,890 Williams Oct. 9, 1934 2,497,521 Trautman Feb. 14, 1950 2,582,191 Curtis Jan 8, 1952 2,795,548 Thomas et a1. June 11, 1957 

1. A LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR PORTION OF A MINERAL LUBRICATING OIL FOR INTERNAL COMBUSTION ENGINES CONTAINING MINOR AMOUNTS OF BASIC ALKALINE EARTH METAL PETROLEUM SULFONATE AND BASIC SULFURIZED ALKALINE EARTH METAL ALKYL PHENATE WHICH IS NORMALLY CORROSIVE TO ALLOY BEARINGS AND A MINOR PORTION, SUFFICIENT TO INHIBIT CORROSION F A P-XYLYLENEDIAMINE SALT OF A DIGLYCOL BORIC ACID IN WHICH THE GLYCOL GROUPS ARE IDENTICAL A-AND B-GLYCOL GROUPS CONTAINING FROM 6 TO 10 CARBON ATOMS IN EACH GLYCOL GROUP. 